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对DRF使用延迟加载

django-rest-framework django python

Bruno Francisco · 技术社区 · 6 年前

我想做一个简单的 lazy loading 使用Django Rest框架。我有一个坚实的背景 Laravel 你可以像这样简单地使用它:

Subscription::with('company')->paginate()

但对于DRF我有问题。一家公司可以拥有 一次订阅 我的模型是这样定义的:

单位

class CompanyManager(BaseUserManager):
    def create_user(self, email, password=None):
        """
        Creates and saves a User with the given email and password
        """
        if not email:
            raise ValueError('Users must have an email address')

        user = self.model(
            email=self.normalize_email(email),
        )

        user.set_password(password)

        user.save(using=self._db)

        return user


class Company(AbstractBaseUser):
    """
        Company refers to what we have referee in the official document as "Empresa Partner"

        Attributes:
            name: The name of the main company
            email: Email to contact the main company
            code: the code attributed to this company
    """
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    email = models.EmailField(unique=True)
    username = models.CharField(blank=True, max_length=100)
    is_staff = models.BooleanField(blank=True, default=False)
    our_system_date = models.DateTimeField(auto_now=True)

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []

    objects = CompanyManager()

    def __str__(self):
        return self.email

class Subscription(models.Model):
    """
    Subscriptions that references the plans and the companies
    :company:
        The owner of this subscription

    :plan:
        The plan this subscription is based on

    :starts:
        When the subscription starts

    :ends:
        When this subscription ends
    """
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    plan = models.ForeignKey(Plan, on_delete=models.CASCADE)
    starts = models.DateTimeField()
    ends = models.DateTimeField()
    created_at = models.DateTimeField(auto_now=True)

我试过用 select_related 根据这个答案 What's the difference between select_related and prefetch_related in Django ORM? 但每次我向端点发出请求时,它都不会显示相关的 Company 的 Subscription

我是怎么用的 选择相关的 :

    def list(self, request, *args, **kwargs):
        queryset = Subscription.objects\
            .all().select_related('company')\
            .order_by('-created_at')
        page = self.paginate_queryset(queryset)

        if page is not None:
            serializer = SubscriptionSerializer(
                page,
                many=True,
            )

            return self.get_paginated_response(serializer.data)

在我的 SubscriptionSerliazer :

class SubscriptionSerializer(ModelSerializer):
    class Meta:
        model = Subscription
        fields = (
            'company',
            'plan',
            'starts',
            'ends',
            'created_at',
        )

0 回复 | 直到 6 年前

Endre Both 6 年前

如果要返回相关模型的字段而不仅仅是其主键,则需要为相关模型定义序列化程序(此处: CompanySerializer )并指示父序列化程序使用它:

class SubscriptionSerializer(ModelSerializer):
    company = CompanySerializer()

    class Meta:
        model = Subscription
        fields = (
            'company',
            # ...
        )